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Planetary RadioDecember 26, 2018

Countdown to Ultima: Alan Stern and New Horizons

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On This Episode
Alan Stern
Alan Stern

New Horizons Principal Investigator, Johns Hopkins University Applied Physics Laboratory

Headshot of Emily Lakdawalla (2017, alternate)
Emily Lakdawalla

Senior Editor and Planetary Evangelist, The Planetary Society

Headshot of Bruce Betts
Bruce Betts

Chief Scientist / LightSail Program Manager, The Planetary Society

Headshot of Mat Kaplan
Mat Kaplan

Planetary Radio Host and Producer

The New Horizons spacecraft will reach faraway Kuiper Belt object 2014 MU69 in the first minutes of 2019. Will the body informally known as Ultima Thule be as mysterious and exciting as Pluto? We’ll hear from the mission’s Principal Investigator, Alan Stern. Senior Editor Emily Lakdawalla takes us through 2018’s biggest planetary science and exploration moments. The coolest asteroid defense stickers in the solar system could be yours if you win the new What’s Up space trivia contest.

Artist's concept of Bennu and Ultima Thule

Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

Artist's concept of Bennu and Ultima Thule
A size-comparison between Bennu and 2014 MU69/Ultima Thule.
Artist's impression of New Horizons encountering 2014 MU69

NASA / JHUAPL / SwRI / Steve Gribben

Artist's impression of New Horizons encountering 2014 MU69

Trivia Contest

This Week’s Prizes:
The full set of five KickAsteroid stickers from the Planetary Society Chop Shop store and a 200-point astronomy account.

This week's question:

In their current orbits, which object gets farther from the Sun at some point, Pluto or 2014 MU69?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, January 2nd at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

How many orbits did Apollo 8 complete at the Moon?


The answer will be revealed next week.

Question from the December 12th space trivia contest question:

As seen from Earth, what extrasolar star (not the Sun) has the largest apparent size in the sky, in terms of angular diameter?


As seen from Earth, the extrasolar star with the largest apparent size is R Doradus. This red giant would extend as far as the asteroid belt in our solar system.


[Mat Kaplan]: Countdown to Ultima this week on Planetary Radio. Welcome. Happy holidays everyone. I'm Mat Kaplan of the Planetary Society with more of the human adventure across our Solar System and beyond. Though officially still known as 2014 MU69, the New Horizons team will tell you that humanity is about to encounter Ultima Thule. The leader of that team, Alan Stern, returns to Planetary Radio to prepare us for a very special New Year's Eve out where the Sun is barely more than just another star in the heavens. First though we'll look to senior editor Emily Lakdawalla for a lightning round review of the biggest events in planetary exploration over the last year. No rubber asteroids just yet but we've got a related prize for the winner of the new What's Up? space trivia contest. Stay with us to hear what Bruce Betts has cooked up this time. Emily, it has been a [00:01:00] busy and very productive year. I'm sorry we don't have more time to spend, the time that all of these different missions and events really deserve. But I know that you will give us a whirlwind tour that is worth listening to. Shall we start with the missions that got underway this year?

[Emily Lakdawalla]: Oh my gosh, Mat. It's been such a busy year and yes, I'm counting four interplanetary missions that got off the ground this year. We had BepiColombo beginning its long journey to Mercury. We had InSight launching and then landing on Mars. We had Queqiao launching to the Moon to serve as a relay satellite for Chang'e 4 which also launched. And finally, Parker Solar Probe which launched in has already begun flying through the outer atmosphere of the Sun.

[Mat Kaplan]: Let's talk a bit more about some of those. I mean InSight not only launched that as you said is has arrived on Mars and has begun to deploy instruments.

[Emily Lakdawalla]: Yes, InSight recently deployed its SEIS instrument, one of its two main science instruments, and should by the end of January have gotten its heat probe on the ground. [00:02:00]

[Mat Kaplan]: When is Chang'e 4 expected to set down on the far side of the Moon? Notably not the dark side.

[Emily Lakdawalla]: Could be within a couple of weeks, possibly in the very first days of January. We'll all be tuned in to figure that out. It's been interesting how much you can watch the activity of that mission through amateur radio telescopes, of all things.

[Mat Kaplan]: Hmm, wow. Some of those spacecraft that we've just talked about had companions and as an organization that deals with CubeSats, let's give them there fair share.

[Emily Lakdawalla]: That's right. Both Queqiao an InSight launched with small CubeSats and both of those CubeSats reached interplanetary destinations, or at least interworld destinations. Queqiao launched with Longjiang-2 which took some photos of Moon and Earth and is now in orbit around the Moon. InSight lost with a pair of MarCO CubeSats that provided relay during InSight's Landing. The MarCOs couldn't go into orbit so they're now in heliocentric orbit and they're still doing science with them.

[Mat Kaplan]: And manage to take a photo or two of Mars as they were [00:03:00] flying past and doing their primary work. Up there on Mars there was a big event last summer. Not one that was a... ended up with happy results, but it did it again show us how dynamic that planet is.

[Emily Lakdawalla]: Well, it depends who you are, if they're happy results. I mean, there is a huge dust storm on Mars and most scientists were just so thrilled to have the opportunity to watch the origin and evolution of a planet-wide dust storm with all of the orbiters that we have up there right now. It was really spectacular for science. Unfortunately, it has caused a lot of problems for the Opportunity Rover which is solar powered. We haven't heard from it for more than six months and hope is diminishing that Opportunity will wake up again. But if this year was the last for Opportunity, it's had a really great want run and you can't have asked for anything more from the little Rover.

[Mat Kaplan]: No, no that is certainly a mission that is well worth celebrating no matter what. We do know that we lost a couple of other spacecraft.

[Emily Lakdawalla]: Yes. Those are Dawn and Kepler both very small [00:04:00] missions, both ended their operations this year, which is bittersweet. Both of those missions served well past their prime missions, got a so much incredible science. They came to an expected end both running out of fuel within a day of each other, was really quite amazing. And so we're going to be digesting the science from those two missions for decades to come.

[Mat Kaplan]: And much science expected from a couple of other missions to small bodies in the solar system.

[Emily Lakdawalla]: Yes this year over the summer we saw two missions approaching their target near-earth asteroids. That's Japan's Hayabusa2 and NASA's OSIRIS-REx approaching Ryugu and Bennu. Hayabusa2 has already set some very small spacecraft down on the surface while OSIRIS-REx is just beginning to do it surveys of Bennu. Hayabusa2 will get some sample from it next year, OSIRIS-REx maybe toward the end of the year. And of course at the end of this year, 2018, we have New Horizons fast approaching its flyby of distant Kuiper Belt object 2014 MU69. It's just been a stunning year, Mat.

[Mat Kaplan]: So much to have been proud of in the past year [00:05:00] and much to look forward to in the new year and Emily, personally, you had a pretty good year as well, didn't you?

[Emily Lakdawalla]: It was a really big year for me too. I published my first book, <em>The Design and Engineering of Curiosity</em> and I've since found out it's the best-selling title in that Springer Praxis field in aerospace and engineering and planetary science and all of those topics. And then I also became the Editor of the Planetary Report. I'm very honored by taking over this magazine that was run for so many years by Donna Stephens and Jennifer Vaughn before her and Charlene Anderson before her and Carl Sagan at the very beginning. So it's quite a mantle to have inherited.

[Mat Kaplan]: And to say very little at least of all of the other terrific content and expertise that you have provided to all of us at where people can read the brand new issue of the Planetary Report. Here on the radio show and in your great blogs. Thank you so much Emily.

[Emily Lakdawalla]: Thank you Mat.

[Mat Kaplan]: That's Emily Lakdawalla, Senior Editor for the Planetary [00:06:00] Society, Editor-In-Chief of the Planetary Report, and our Planetary Evangelist. We are about to pay a brief call on 2014 MU69 or Ultima Thule, call it what you like. Its discovery in January of 2014 must have generated a sigh of relief from New Horizons Principal Investigator Alan Stern. This little world, so much farther from the Sun than Pluto, would be within reach of the spacecraft that was then still speeding toward its historic 2015 encounter at Pluto. I just called it a little world but Ultima is a thousand times bigger than Comet 67p that was visited by Rosetta. We know it is either elongated or possibly two [00:07:00] bodies near are even in contact with each other. We know it is reddish and we know it takes nearly 300 years to make one orbit. And that's about it. At least until New Horizons brushes by. That will happen at 05:33 UTC, or 12:33 a.m. Eastern, on New Year's morning 2019. I'll be at the Johns Hopkins University Applied Physics Lab outside Baltimore, Maryland. That's where Alan and his team will be anxiously counting down to the flyby. New Horizons won't care if the US federal government is still shut down on that morning, but you might if you hope to follow the encounter. NASA TV will not provide live coverage unless Congress and the Trump Administration have found a solution for the budget impasse. Alan told me APL will step in with its own live coverage, if it must. We talked in the early morning on December 24th, just seven days before the encounter. Alan, welcome back. I am so [00:08:00] thrilled to be looking forward to joining you at the Applied Physics Lab in just a few more days for this absolutely amazing encounter with this object known as 2014 MU69, though I much prefer the name that you and your team have given it.

[Alan Stern]: Ultima Thule?

[Mat Kaplan]: Yes.

[Alan Stern]: Yeah. We are so excited about this flyby and can't wait to have you here. And are just barreling towards New Year's Eve and New Year's Day with the close approach. It's going to be spectacular.

[Mat Kaplan]: I can barely get over the fact that we didn't even know that this little world existed less than five years ago. What's the current status of the spacecraft? And the mission?

[Alan Stern]: Well, the spacecraft is on final approach. We passed the point where we will make any more trajectory corrections. We are just spot-on in terms of navigation, spacecraft's very healthy. All the instruments are operating well. [00:09:00] The command load instructs the spacecraft, the highly choreographed set of instructions for the entire flyby operation, is not only up on the bird burned into the flash memories of the two primary computers, it's already engaged. So we're already in the second day of the flyby operations.

[Mat Kaplan]: Wow. Take us back to when New Horizons had its encounter with Pluto. It sounds like this one is a little bit less exciting in very good ways.

[Alan Stern]: At first I wasn't sure what you meant.

[Mat Kaplan]: Yeah. I thought it might be a little confusing.

[Alan Stern]: I think I got you. Yeah, we had a little Fourth of July fireworks on the Pluto flyby when our main computer went offline and the spacecraft backup computer took over and cut off all communications with the Earth and gave us a very intense three-day homework assignment of putting Humpty Dumpty back together again. But you know, we have a really [00:10:00] spectacular mission operations and engineering team. This is the Apollo 13 of planetary exploration what happened to us and they rescued it. We're working round the clock for those three days and we didn't miss one single close approach observation as a result of their spectacular save. This fly by so far has been going just perfectly by the textbook. We've not had any kind of problems, anything like that.

[Mat Kaplan]: It really was a spectacular save. I mean, that's the right word for it and it is so well documented in that book that you co-authored with David Grinspoon, <em>Chasing New Horizons</em> that we've talked about previously on the show. So, still recommending that book as a great read about this mission. But the mission continues. Take us back once again, though, even before that that rescue when you were still looking for a Kuiper Belt object to explore. It was quite, wasn't it?

[Alan Stern]: It really was. Let me start [00:11:00] by giving some context to those who might not know it. The real reason that this mission was funded was because we were at the top of the 2003 decadal survey in terms of scientific priorities for planetary exploration. And the reason that happened was the discovery the Kuiper Belt and what the National Academy wrote in that decadal survey was that the discovery of the Kuiper Belt, this third zone of the Solar System that has so many forensic clues to the origin of the planets and which is dotted with other dwarf planets beyond Pluto, raised that priority and as a result when we proposed this mission and competed to win it, NASA required that all of the competing proposals build a spacecraft that was capable of not just flying to explore the Pluto system, but onward deeper into the Kuiper Belt to do Kuiper Belt flybys. Do just exactly what we're doing with Ultima Thule on New Year's Day 2019. [00:12:00] So we're pretty excited. This is the capstone portion of the mission. We can talk a little bit more later about the fact that we hope to do one more Kuiper Belt object fly by still farther out in the 2020s, but this is a first look anyone has ever had up close at this kind of body and we just can't wait to start getting the data back.

[Mat Kaplan]: As I said, we didn't know it was there, you're coming up on the fifth anniversary of its its discovery which was quite a feat in itself. I mean this thing has an apparent magnitude, I have read, of about 27 which for those who aren't familiar with those numbers is... that's a very very faint object. Was this a kind of a worldwide effort to find this target?

[Alan Stern]: It really became that, we started searching using the largest ground-based telescopes in the world like the Keck and Gemini South and others, Subaru in particular, back in 2011. [00:13:00] And year after year after year we were awarded observing time and search with all those telescopes and we found dozens of small Kuiper Belt objects along our flight path, but none were within our reach, within our fuel reach. And when things started getting desperate in late 2013 as it turned into 2014 I made the decision that we should apply to the Hubble, and we had to ask for really significant amount of time, almost 200 orbits. But the Hubble awarded us that time and that did the trick. Within a space of two weeks the Hubble found three targets that we could reach from which we selected Ultima.

[Mat Kaplan]: What followed was I think yet another exquisite feet of navigation by your team to put you on course for a for Ultima Thule, right?

[Alan Stern]: Well, that's right we use the Hubble the entire four years from the time we discovered Ultima in the Summer of 2014 until August of this year [00:14:00] when we could spot it with our own telescopes. Now think about this, the Hubble was taking measurements of Ultima moving against the star field. From that we could compute its orbit and then we could compute the intercept engine burns that we had to do to get off the Pluto trajectory after Pluto and to intercept Ultima. But think about this, here's this small body, ten thousand times less surface area than Pluto, about the size of Greater New York City. Its reflectivity is about that of garden-variety dirt, it is illuminated by a Sun that is more than 2,000 times fainter than it is here on Earth, about the equivalent of moonlight. And the Hubble is capable of routinely spotting it and tracking it accurately. It's just amazing.

[Mat Kaplan]: It sure is. As we speak, you're still a few days out. What have we learned at this point? I mean, it's still not much more than a point [00:15:00] of light, right? And and I'll remind folks that we're talking on December 24th, Christmas Eve.

[Alan Stern]: That's right. We're about a week out. We're closing at almost a million miles per day. But Ultima is still just a dot in the distance. We won't resolve it until a day before the flyby and we won't see it well until hours before the flyby. So far, all we know is that it doesn't have any distance satellites. We can't tell about the really really close in ones that might be there. Same for rings, doesn't have any distant rings, but it might have dust assemblages or rings in really close. We'll find that out in less than a week. But Ultima's been guarding her secrets pretty well. We expected by now to be able to see the periodic fluctuations in brightness as it rotates, but we still haven't been able to pin that down and we're not sure why. It's not because the cameras aren't working. It's because there's something about Ultima or the Ultima system that is masking that [00:16:00] signal because we know from ground-based stellar occultations that painted out its silhouette, Ultima is not spherical. It has a very irregular shape. Looks kind of like a contact orbiting binary so it should display a strong light curve, but we can't find it and we're getting very close now and we look at other Kuiper Belt objects with our cameras that are farther away and they do show those light curves. So it's a puzzle but we're going to solve it next week.

[Mat Kaplan]: I'm so glad you brought this up because you did this announcement was just made to the media on December 20th of this really odd thing. And in fact, you called it Ultima's first mystery in the press release that I got. And I guess there's already some hypothesizing about what could be causing this because it really, it really ought to be flashiness a little bit right? This this light curve ought to be curved.

[Alan Stern]: It ought to be but it's not we have some crazy ideas and maybe one of them is [00:17:00] right maybe none of them is right, you know, for example, if the pole, the rotation axis is pointed straight at us then as it rotates it doesn't change its profile and there would be no light curve. But that requires a special pointing geometry. Why should it just happen to be pointed in our direction? So maybe instead it's got a lot of small satellites in close and they're all tumbling and producing a signal that masks the light curve of Ultima itself. Or maybe it's enshrouded in dust, you know, so the shape can be seen in an occultation, but the light curve is muted and those are long shot explanations. But we're really grasping here. It's been a long time since we've done something like this, fly up to an object that we know essentially nothing about. It's surprising that we didn't see the slight curve weeks and weeks ago and even as we get closer and closer Ultima keeps guarding those secrets. Stay tuned.

[Mat Kaplan]: And this brings up this wonderful theme which [00:18:00] has run through all of Planetary Exploration, maybe all of science, which is that there are always surprises ahead. I can't think of a mission that has not uncovered mysteries and and it sounds like you fully expect that not just with this one about the light curve but maybe mysteries that are still just a few days ahead of us.

[Alan Stern]: Well, absolutely. What is ultimately made of? How homogeneous or heterogeneous is it? What is its geology like? How is it assembled? Does it have satellites and rings as I said a little earlier. Does he even have an atmosphere? We are bringing this spectacular battery of seven very high-tech instruments to bear to learn everything we can as we flash by it on a, you know, one shot, all-or-nothing flyby on next Monday and Tuesday. By mid-week next week as the data starts to rain down. We're going to for the first time see a whole new class of object. These Kuiper Belt [00:19:00] objects form so far from the Sun and kept nearly at absolute zero for billions and billions of years. A lot of us think that Ultima will turn out to be a time capsule from the earliest days of the era of planet formation and have a great deal to teach us about how that accretion got going. I just can't wait.

[Mat Kaplan]: My colleague Emily Lakdawalla feels the same way. She has created a really excellent guide to the encounter. It's a December 17th post to the Planetary Society blog and we will link to it from this week's show page at along with the excellent Applied Physics Lab New Horizons Mission website. But can you give us a just a very brief look ahead at the major events that are coming in the next barely a week?

[Alan Stern]: Yeah, well, we are already using the cameras on board to study Ultima even as a dot the distance to look for those light curve variations, which will eventually reveal [00:20:00] themselves to search for satellites. We do that almost every day now on final approach. Same for rings. Beginning about a day before we'll start making color measurements and then we'll make a spectroscopic measurements to both search for an atmosphere and determine what the surface of Ultima is made of. Meanwhile our charged particle plasma sensors will be looking for interactions between Ultima and the solar heliosphere. And our dust instrument which counts impacts on the spacecraft will be looking for any direct signs of dust as we make the approach. And then as we get close in the last hours before closest approach and then at closest approach and as we make the initial exit from the system, we'll do all the high-resolution observations that will ultimately result in megapixel class images, color images, resolved spectroscopy of the surface so we can see if the composition varies from place to place. We'll watch the Sun and a couple of ultraviolet bright stars [00:21:00] pass near Ultima to search for any gas absorption features in the ultraviolet spectrum that would reveal a coma or atmosphere around it. We're even going to map it in stereo, so we get a 3D stereoscopic topography map out of the flyby. And in the end because we're going much closer than we went to Pluto we'll have much better surface resolution on the target. The images should just be spectacular and from a scientific standpoint I don't think that when we started this mission we thought we would be able to do as well as what we've got planned. So we're pretty excited.

[Mat Kaplan]: But we're going to have to wait a little bit beyond the encounter, right, to see those... the best of these images that are taken during the closest approach, and can you explain why that is?

[Alan Stern]: Well, you're absolutely right, Mat. The day after the flyby on January 1st, the spacecraft will down link an image that's a hundred pixels across and about 10,000 pixels on the target and within [00:22:00] 48 hours after that we'll have an image with 40,000 or so pixels on the target. But the megapixel class images won't be down until February and here's why: as we pass by at 32,000 miles an hour, we have some uncertainty due to navigational challenges of having only discovered Ultima and tracked its orbit for four years about 1% of the orbit period. As a result, we have to actually shoot several hundred images in rapid succession along a track, and Ultima will hopefully be somewhere along that track, but we don't know where. So we're bracketing if you will, we're spatially bracketing where Ultima might be. And then from the lower resolution images that will come down just after flyby. We can mathematically predict which images in that track to go and get and downlink, the high-res, of Ultima. But by the time we get those to the ground and do that work and [00:23:00] then you line all those things up and you count the fact that our spacecraft is going behind the Sun January 4th as seen from the Earth, cutting off communications for a period of time, it's going to stack up to be February before we get these really juiciest images on the ground.

[Mat Kaplan]: Wow. It is a reminder of just how difficult, how complex a mission like this is and how long will it be before we get all of the data from New Horizons that it has collected during this brief encounter?

[Alan Stern]: Well, it's going to be quite a while. The data sets from this flyby are going to be coming down every week for 20 months until August or September of 2020. You remember Mat for Pluto it took us 16 months to get all the data back. We're taking just as much data. We're filling those solid-state recorders with all kinds of different data types and we'll prioritize them to get the most important stuff home first, in part because we want to write as a action-packed and you know, scientifically [00:24:00] productive first papers as we can with the results, but also that's an insurance policy against something bad happening where we couldn't get all the data, at least we've got the most important stuff first.

[Mat Kaplan]: Perish the thought, let's hope that things go as perfectly and as wondrously as they did with Pluto. You started to talk about New Horizons future, I'll note that we only just a few days ago celebrated the passage of Voyager 2 beyond our Solar System's heliopause, which put it in interstellar space more or less. What is ahead for New Horizons?

[Alan Stern]: Well, we're currently on a five-year first extended mission that lasts through 2021. The centerpiece is the flyby of Ultima, but it also includes context observations were making more than two dozen other Kuiper Belt objects near our flight path. And heliospheric measurements that we make almost around the clock, and we'll do all that through 2021 and get all the data back. But in 2020, we're going to propose a new [00:25:00] extended mission going out even farther. You know, the Kuiper Belt extends out 70 times as far from the Sun as the Earth is. Ultima's is only forty four times as far out as the Earth-Sun distance. It'll actually be the late 2020s in the year 2027 or 2028 before we leave the Kuiper Belt. And we want to be productive throughout that period so we'll propose to continue Kuiper Belt studies and to look for new flyby targets. After all there's no other spacecraft exploring the Kuiper Belt and right now there's none being built to come after us. So this is the our chance and we want to really milk this mission for everything it's worth. And we have the power and fuel to fly on throughout that period and even longer.

[Mat Kaplan]: Do you expect that like Voyager 1 and Now Voyager 2 we will be talking, with hearing from New Horizons right out beyond the heliopause out into interstellar space?

[Alan Stern]: Well, that's not as [00:26:00] good a story as the Voyagers and I'll tell you why. First of all, we only have one RTG, the Voyager carried two that with the plutonium power supply that we have a board. We can probably operate into the mid to late 2030s not longer. At that point will be about 90 astronomical units from the Sun maybe a hundred if we can find the right power saving moves to go a little further. But the heliosphere actually changes its distance from the Sun, it breathes in and out with the 11-year solar cycle. The foragers crossed out into interstellar space at about a hundred and fifteen times as far away as the Earth is from the Sun. If that's where the heliosphere is when we run out of power we won't be able to get that far. But if it's in a contraction phase, you know, sometimes it's as close as 80 or 90 astronomical units, then we will be out in interstellar space and currently here in 2018 the models just aren't good enough [00:27:00] to predict where in the solar cycle and how strong is solar cycle will be happening in the late 2030s. So we can't predict which side of the heliopause New Horizons will be on in those years. As we get closer we should be able to do that. But for now, we're just going to keep exploring going farther and farther out. We have instruments like Voyager does but much more sophisticated because they were built a generation later with much higher technology of the early 2000s. So they're much more sensitive to studying the heliosphere and then if we get there into the interstellar medium.

[Mat Kaplan]: I'm going to put my money on New Horizons and I'll try to wait patiently into the 2030s, but let's leave New Horizons to its destiny for the moment. There was another announcement that you and a team at the Southwest Research Institute made just a few days ago that has shown that it's possible we could send [00:28:00] another mission out toward, well, let's talk about Pluto first, with electric propulsion, otherwise known as ion engines, that really could do something even more amazing at Pluto and possibly beyond and I'm sure you know what I'm talking about.

[Alan Stern]: Well, I sure do and I'm glad you asked about it, Mat. Yes, we have a team at Southwest Research that's looking at follow-up missions to Pluto. We made some pretty spectacular advances. We found that using launch vehicles that already exists or are being built and will be flying early in the next decade and with electric propulsion no more advanced than what the Dawn mission so spectacularly exploited to go to Vesta and Ceres that we can not only fly a mission to orbit Pluto, but we can use Pluto's big satellite Charon to do the entire orbital tour. All of the maneuvers that would have taken propulsive [00:29:00] ability can now be done with gravity assist flybys of Charon to dip down in the atmosphere and to make close flybys and each of Pluto's small satellites and to do all the other scientific objectives. That's quite a breakthrough, but the cherry on top is that Charon's gravity and an ability to do gravity assists is so great that we can even use Charon to get back out of orbit after several years at Pluto and go back into the Kuiper Belt and go on exploring. In fact, what our team has found, and this is really something, is that you could send a Pluto orbiter out and after it leaves Pluto orbit it can make flybys of other dwarf planets. In some cases it can even enter orbit around a second dwarf planet the way Dawn did with Ceres. So we no longer are in this kind of a Hobson's choice of deciding do we want to explore the diversity of dwarf planets in the Kuiper Belt or go back to [00:30:00] Pluto and study it in more depth. Our breakthroughs that we can do both with one mission in one spacecraft and that's really game-changing.

[Mat Kaplan]: Marvelous work Alan, giving us even more to look forward to but what I'm most looking forward to is what's just a few days away as we speak. I will say it again. I said it at the outset. I am absolutely thrilled to be joining you at the Applied Physics Lab there in Maryland when New Horizons has this encounter with Ultima Thule. Best of luck to you and the team, the greatest of success to all of you and cannot wait to have this encounter.

[Alan Stern]: Thank you, Mat. I'll pass that along and can't wait to see you here. We are so looking forward to New Year's Eve and New Year's Day and hope that all your listeners will spend your New Year's with NASA and follow this incredible flyby.

[Mat Kaplan]: I suspect a lot of them will be right there with us. We have been talking with the Associate Vice President at the Southwest Research [00:31:00] Institute and Principal Investigator for the New Horizons Mission, Alan Stern. He is also the co-author with David Grinspoon of that great book <em>Chasing New Horizons</em>, and he and his team are about to experience a second encounter where no one has gone before, at this little object they call Ultima Thule. It is time for the last What's Up? segment of the year here on Planetary Radio. Bruce Betts is the Chief Scientist for the Planetary Society and he is back as he is every show. Welcome. Tell us about the night sky and all that other great stuff you've got.

[Bruce Betts]: All right. Pre-dawn you got Jupiter looking bright and Venus looking super bright over in the East before sunrise. And in the evening sky southwest got Mars looking reddish. You can check out in the evening, east, Orion is now fully up and if you follow Orion's Belt down towards the horizon in the evening you will find Sirius, the brightest star in the sky. The night sky that [00:32:00] is. We've got a partial solar eclipse. Excited, Mat?

[Mat Kaplan]: Always.

[Bruce Betts]: So then I guess you'll be road-tripping to parts of Eastern Asia or the Northern Pacific Ocean.

[Mat Kaplan]: I'm happy for them.

[Bruce Betts]: I am too. That's January 6th, and we've got a total lunar eclipse will talk about that more later in the month. And then we've got the always hard to pronounce Quadrantids meteor shower peaking on the night of January 3rd and 4th. The good news is there's no Moon that night. It's new Moon basically, so it's good to view and they can be good. But they're it's a pretty sharp peak so you're pretty much looking mostly at that night, maybe a little bit day or day before day after but ideally the night of the 3rd and the 4th. Not as good as Geminids traditionally, but still pretty good shower.

[Mat Kaplan]: Did you get anything out of the Geminids?

[Bruce Betts]: Yes, a cold. Oh, actually I already had it which is why after telling everyone to go see it I just laid around feeling miserable inside.

[Mat Kaplan]: Yeah, I'm sorry.

[Bruce Betts]: It's a good time. But you know, they'll be back. So maybe I'll try the Quadra... the Q shower.

[Mat Kaplan]: A shower of Qs. Yeah.

[Bruce Betts]: We move onto this week in space history. It was 1801 the Giuseppe Piazzi discovered Ceres, which was called a planet and then an asteroid and now a dwarf planet and Dawn really found really cool stuff at it that was 1801, first asteroid discovered. We move onto Random Space Fact.

[Mat Kaplan]: Little trouble getting started there. I think you might need a boost.

[Bruce Betts]: For you Mat. I worked out a scale model. So New Horizons at the time of its flybys... well, let's start our [00:34:00] tour, we're going to put the sun in Los Angeles because I don't know.

[Mat Kaplan]: That's where it belongs.

[Bruce Betts]: We wouldn't even... the distance to Earth on this scale, we wouldn't even make it out of the LA megalopolis. We'd be roughly in San Bernardino for Earth. Jupiter which it flew by many years ago and it flew by there, it's kind of like the distance from LA to Las Vegas or maybe just a little bit farther. And then Pluto. Pluto in Chicago to within ten percent. So LA to Chicago. And now 2014 MU69, LA to New York. LA, San Bernardino, it sounds like it could be a song. LA, San Bernardino, Las Vegas, Chicago, and now New Horizons will get to New York.

[Mat Kaplan]: Excellent. Yeah, that's a great comparison. Thank you.

[Bruce Betts]: You're welcome. All right, we move on to the trivia contest and [00:35:00] I asked you, as seen from Earth, what extrasolar star has the largest apparent size? In other words largest angular diameter as seen from Earth. How do we do, Mat?

[Mat Kaplan]: You threw a lot of people who were pretty sure that it was that famous star Betelgeuse, which a movie was not named after, but it is no longer. Apparently it was at one time Betelgeuse, but is now something called R Doradus. Do you, do you have any information about this star?

[Bruce Betts]: I do but I can't tell you about it. It's secret. No, it's not secret. Yes R Doradus, known also is HD 29712, is the name of a red giant variable star in the constellation Dorado, which is in the far Southern Sky. Distance from Earth is 178-ish light years. [00:36:00] So still kind of far but it's so dang huge. How huge is it? Well, let me tell you Mat. If it were placed at the center of our Solar System the orbit of Mars and most of the main asteroid belt would be contained within the star.

[Mat Kaplan]: Oh my that's a... that's a big star.

[Bruce Betts]: My my that's a large star.

[Mat Kaplan]: That's a bigger star than George Clooney.

[Bruce Betts]: Ah.

[Mat Kaplan]: Phil Crane of Sacramento, California.

[Bruce Betts]: Yay.

[Mat Kaplan]: He said it was R Doradus and that makes him our winner. So Phil congratulations. You got that copy of the National Geographic Space Atlas mapping the universe and beyond and the National Geographic Almanac 2019, two beautiful books. That space atlas is really gorgeous and you're going to want to leave it out so that you can impress people at your New Year's Eve party or whatever. But it is a great set of books from Nat Geo and we thank them for providing these. [00:37:00] And as you might expect we got some other great stuff. Nick Cherie in Scotch Plains, New Jersey. He says R Doradus is one weird star. 370 times the Sun's radius, but the mass is only slightly greater than our Sun. It's actually, I won't give you the numbers, but the mass is way less than the mass of our atmosphere at sea level. He says in short this star is mostly almost a vacuum. Which, how is that even possible?

[Bruce Betts]: You mean density is similar to our atmosphere? Average density?

[Mat Kaplan]: Yeah, apparently quite a bit less than our atmosphere on average.

[Bruce Betts]: Yeah. But not the mass. This is the mass of a good sized star and that is possible because you're spreading even though you have a huge mass you're spreading it out over an enormous volume. Hard to comprehend volume going out. Weird weird stuff. That's what happens with red giants end of life, you take a sun-like star or [00:38:00] similar and then it expands outward a long ways and spreads out the density.

[Mat Kaplan]: That explains it. Brendan Petracheck in Winnipeg, Manitoba. You had mentioned that this star is in the far Southern sky. He says, is it just me or is the coolest stuff in the night sky only visible from the southern hemisphere?

[Bruce Betts]: It gets spread around.

[Mat Kaplan]: But his conclusion won't bother Richard Nielsen at all because Richard is in Brunswick, East Australian. He says that if you want to get an idea of the angular diameter of this star as seen from the surface of Earth, ask an astronaut on the International Space Station when it passes over to hold out the palm of his hand and that's about it, or if it were an American football field a hundred yards or you know little less than a hundred meters on the surface of the Moon. That's that's about how wide this thing appears from Earth. Pretty good, right?

[Bruce Betts]: Wow.

[Mat Kaplan]: Bill Edrington, [00:39:00] Searcy, Arkansas. He says, I felt like R Doradus after my Thanksgiving dinner.

[Bruce Betts]: And now the holidays are coming up again, so go red giant.

[Mat Kaplan]: Finally not from our usual Poet Laureate but from Jim Mackenzie in Regina Saskatchewan. He says, I was going to answer in manner obtuse that yes, the right answer is old Betelgeuse. But research is key and I'm no ignoramus. I used Google fu and I found R Doradus. Not bad. Not bad. Don't worry, we're not switching away from our our beloved Poet Laureate, but I just thought that that was worth mentioning. What's also worth mentioning is that we have yet another contest.

[Bruce Betts]: We do and as a gift for the end of the year and New Year, there will only be two choices or at least only two good choices to answer this question. In their current orbits, which [00:40:00] object gets farther from the Sun at some point in its orbit: Pluto or 2014 MU69? So not where they are now, but we're who gets farther away from the Sun. Go to

[Mat Kaplan]: You have until Wednesday January 2nd at 8 a.m. Pacific time to get us the answer to this one. And if you get that right and are chosen by, we got a 200 point account for you. By the way, we also have that for this week's winner along with the Planetary Radio t-shirt from But in addition this time instead of a t-shirt from Chop Shop, you know, we work with Chop Shop to create this great stuff that is part of our Kick Asteroid campaign, which you have a lot to do with, right? Because this is planetary defense, which is a part of your bailiwick at the Planetary Society.

[Bruce Betts]: Yes. I worked with Thomas Romer there [00:41:00] in the design of all the items.

[Mat Kaplan]: And they're great. If you go to Chop Shop Store,, you'll see these, you can check them the Planetary Society store. We will send you all of these stickers: a logo sticker, three that are just really fun impact stickers including at least one with the dinosaur, and a stay extinct sticker...

[Bruce Betts]: Stay UnExtinct.

[Mat Kaplan]: Stay UnExtinct. He wrote it wrong on here. I read it. It's your fault Thomas. A Stay UnExtinct sticker.

[Bruce Betts]: All right, everybody go out there, look up the night sky, and think about all the wonderful things you want to see in the night sky in the new year. Thank you. Good night. Happy New Year everyone.

[Mat Kaplan]: Happy New Year, Bruce. He's Bruce Betts, the Chief Scientist for the Planetary Society, who joins us every week in this new year for What's Up? Planetary Radio is produced by the Planetary Society in Pasadena, California and is made possible by its members who live on the final [00:42:00] frontier. MaryLiz Bender, our Associate Producer. Josh Doyle composed our theme which was arranged and performed by Pieter Schlosser. Help us share the passion, beauty, and joy: leave a rating or review for Planetary Radio where others will find it. I'm Mat Kaplan.

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Listen more: near-Earth asteroids, trans-neptunian objects, interview, mission status, podcasts and videos, astronomy by planetary missions, asteroids, Planetary Radio, asteroid 101955 Bennu

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